In a small but substantial way, the terrorists have won. True, America's immensely powerful military forces have destroyed Afghanistan's appalling Taliban regime. And they have apparently backed Osama bin Laden -- the evil mastermind behind the Sept. 11 attacks -- into a remote province along the Afghan-Pakistani border.

But meanwhile, back at home, a terrible price has been paid. Before the fanatical attack on the United States 34 months ago, Washington was unquestionably the most open capital in the world.

For generations, the White House opened its great iron gates every weekday morning to thousands of tourists, domestic and foreign alike. The Capitol building, too, offered tours, but curious visitors were also free to explore the main building on their own. The FBI had its tours, as well, the highlight being an ear-popping demonstration on the use of firearms in the sound-proof basement of its Pennsylvania Avenue headquarters.

Even the prim Pentagon allowed escorted hour-long tours of the building - - complete with detailed brochures in five languages, including Chinese and Russian.

Visitors were welcome to sit in on hearings of the Supreme Court, and the Treasury Department happily showed sightseers how it printed currency. Even the supposedly super-secret CIA, its headquarters located in nearby leafy McLean, Va., had a highway directional sign reading "Central Intelligence Agency next exit."

Today, much of this beguiling traditional democratic American openness has been rudely swept away, possibly never to return. And the nation once known as "the land of the free and the home of the brave" seems both less free and less brave.

Whether the Bush administration has badly overplayed the fear of the possibility of future threats is a matter of heated debate (and is becoming a crucial question in the presidential-year elections).

But one thing is certain: Washington today is a heavily armed, hunkered- down capital. The city on the Potomac appears to be a city under siege. Congress has allocated more than $600 million for increased security for the capital.

Police cars and SUVs with tinted windows constantly patrol the National Mall, stopping passing trucks for random inspections. Sniffer dogs roam the Senate Office building. Capitol police use mirrors to check for bombs hidden beneath the cars of staff people who work there. Helicopters watch the sky. And Ray-Ban-wearing sharpshooters are seen openly walking the White House roof.

Under the city's streets, inside the Metro stations, recorded announcements appeal to passengers to report anyone who looks "suspicious." Everywhere one looks, huge concrete barriers have been set up -- encircling the Capitol, in front of the State Department, around the national monuments, and near dozens of federal office buildings.

Some defensive obstructions have been disguised as giant flower planters, but others are simply ugly concrete blocks, known as "Jersey barriers," which now mar many of the broad avenues of the once elegant southern city surveyed by George Washington in 1791. Noted Washington architect Arthur Cotton Moore calls the multiple, mismatched layers of concrete protection "a trashing of the city ... We are creating a monument to the Jersey barrier."

Visitors to the capital are quickly made aware of Washington's wartime stance. Even before boarding their Washington-bound plane, most travelers have to step out of their shoes and pull off their belts in order to pass through metal detectors to get on their aircraft. Pilots tell passengers bound for Reagan National Airport that federal law forbids them from leaving their seats during the last 30 minutes of the flight. Should you disregard this directive, and stand up, the flight will immediately be diverted to another airport. Every commercial airliner flying into the capital carries an armed U.S. air marshal. Their identity is meant to be secret, but they are easy to spot. Well- built young men sitting in business-class aisle seats, they wear open sports jackets and have magazines in their laps, which they never seem to read. Considering the scale and deadly ruthlessness of the attacks on the World Trade Center and the Pentagon, it may seem difficult for critics to accuse the Bush administration of excessive emphasis on security.

Those familiar with Washington may recall paranoia surfacing, albeit not on this unprecedented scale, during the tension of the Cold War years. Yet in the past, Washington had remained completely open through four presidential assassinations, eight attempts on the lives of presidents, a Civil War that raged only miles away and two world wars. But now, it is closed. All because of 19 men, armed with box cutters, who were able to enter the country only because of incompetent immigration officials. To continue to close off the nation's capital to the very people to whom it belongs seems both unwarranted and misguided, say a growing number of critics. The need for common-sense vigilance, they say, has now slipped into ugly paranoia.

The grassy area in front of the south lawn of the White House, known as the Ellipse, was once a favorite place for Sunday touch football games played by Georgetown University students, and a choice photo spot for tourists. Today, it is now largely a part of the White House's security zone, which the Secret Service calls "the box." Legally, the Secret Service has virtually unlimited discretion to do what it feels necessary to protect a president, and there is talk of expanding the security zone around the White House to include Lafayette Park, which faces the north side of the White House and has been a place of giddy protest for generations.

The section of Pennsylvania Avenue fronting the White House is already closed, and the north lawn of the mansion can now be seen only through a 6- foot chain-link fence. Just a few hundred yards from the White House, across Constitution Avenue, the Washington Monument is encircled by an ugly 10-foot gray wall. Officials say it's only temporary and will be taken down once a more permanent and less intrusive earthen wall is constructed.

Perhaps the most dramatic change has been the extensive redevelopment of the Capitol grounds. It was once a splendid bucolic setting of century-old oak trees and slopes of Bermuda grass, where this writer once enjoyed reading the Sunday papers on a picnic blanket, and where friendly passing National Park Police would look the other way if they spotted an open beer bottle -- an offense in Washington. Today, the grounds are being torn up to make way for a new underground visitor's center, which will include sweeping new security measures. The outer perimeter near the surrounding streets have been lined with a series of concrete barriers.

Closer in, a wooden wall and chain-link fencing have been thrown up around the Capitol itself, preventing walkers or joggers from stepping onto the grounds except at the main entrances.

The overall effect suggests that security planners want to transform the Capitol (known historically as "the people's house") into an enclosed facility like a military base with specific points of entry, where only people with the right papers, or with appointments, will be permitted to pass unsightly security huts.

"Trying to have an open city is hard," Washington Mayor Tony Williams said recently. "But our city is a working symbol of democracy. We could make it really a lot safer by putting Jersey barriers around everything, but then we wouldn't have much of a city to protect."